1. Field of the Invention
This invention is associated with earth-working equipment such as back hoes, pull shovels, dippers and the like, useful for digging holes and trenches in the earth. The invention is particularly directed towards a hydraulically powered excavating structure adapted for mounting on a flat-bed truck or similar vehicle. The excavator is primarily adapted for digging vertical shafts with straight sidewalls, but may also be used for digging trenches.
2. Description of the Prior Art
A past art search was conducted at the U.S. Patent Office on the above referenced subject in the following U.S. classes and subclasses: 414/694, 695.5
The following patents are noted as being most pertinent to my invention:
1. U.S. Pat. No. 4,257,731 teaches a back hoe type machine. This particular excavator has a boom attached adjacent the digging implement extending from the digging implement at an angle. The angle of the boom would cause the boom to hit the top edge of a vertical shaft limiting the possible depth of the shaft.
2. U.S. Pat. No. 3,351,221 teaches a towable back hoe device which might be used for digging a shallow vertical shaft, however it is primarily designed for excavating graves.
3. U.S. Pat. No. 2,927,706 teaches a hydraulically-operated dipper having a rotatably affixed dipper or bucket.
4. U.S. Pat. No. 2,784,855 teaches a boom mechanism for digging machines. The boom is generally horizontal tubular telescoping arrangement using a hydraulic ram to raise and lower a generally vertical bucket arm. The raising and lowering of the bucket arm with attached bucket changes the angle of the telescoping boom.
5. U.S. Pat. No. 2,411,498 teaches a pull shovel having a telescoping bucket support structure. The pull shovel is operated using a combination of hydraulic rams, cables and pulleys. This digging device appears well suited for trenching but would not work well for vertical shaft digging due to the angled position of one pull cable which would hit the upper top edge of a vertical shaft.
Of the above examined patents, none were considered to be physically structured similar to mine and none appeared to be as well suited for both deep vertical shaft digging and horizontal trenching.